Evaluation of Aortic Hemodynamics and Compliance in Aortic Stenosis

项目摘要 二尖瓣主动脉瓣(BAV)是最常见的先天性心脏病，易患先天性心脏病。 并发症，如主动脉狭窄(AS，最常见的原因)和主动脉瘤。当前的指标是 对BAV和TAV患者及其伴发AS的区分不力，对AS的处理不力 在目前的指南下，BAV和三叶主动脉瓣(TAV)的患者几乎是相同的。当前临床 护理包括超声波和CT或增强MRI以生成血管造影，以及外科手术 阈值是基于升主动脉的直径和生长速度。这个项目的目标是 开发高分辨率自导航bSSFP序列，并将其与4D流动数据结合在一个 自动化管道，可改进大动脉的解剖和血流动力学特征。 而4D Flow是我们实验室首创的方法，可以获取时间和空间分辨率的3D流 在不使用对比度的情况下，通过将更高分辨率的扫描与 改善了血液组织对比度。4D血流数据显示AS患者的主动脉容量 从历史上看，由于高速流动喷射器的存在，单独使用也更具挑战性。临床 4D流的翻译也受到时间密集型分析工作流的限制，因此此项目包括 序列开发的目标以及开发基于云的自动化分析管道的目标 数据。与临床医生的密切合作将确保计算的指标是相关的，并以 可能对这些患者的临床分期或治疗有用的方式。 这个提议的第一个目标是发展和验证平衡的稳态自由进动。 (BSSFP)序列收集改进的解剖数据，分辨率高，血液组织对比度提高 测量升主动脉的直径，并在以下几个时间点进行主动脉分割 心脏周期。这将允许计算相对面积变化作为主动脉顺应性和 心动周期内壁切应力动态变化的检查。第二个目标将包括这一点 将更高分辨率的数据和4D流数据传输到高度自动化的管道中，从而实现快速分割 并计算了主动脉壁剪应力的动态变化和相对面积。在第三个目标中，20个BAV 从西北大学的患者群体中招募20名患有AS的TAV患者，然后进行成像和 使用新协议进行了分析。这将证明在临床环境中使用该方法的可行性， 同时也有助于回答AS在BAV和TAV患者中是否是一个独立的临床实体的问题。 临床合作者将帮助指导该项目实现改善临床成像和 对这些复杂的患者进行分期。

Project Summary Bicuspid aortic valve (BAV) is the most common congenital heart defect, and it predisposes patients to complications such as aortic stenosis (AS, most common cause) and aortic aneurysm. Current metrics are ineffective at distinguishing patients with BAV and TAV and concomitant AS, and management of AS in patients with BAV and trileaflet aortic valves (TAV) is nearly identical under current guidelines. Current clinical care involves ultrasound as well as CT or contrast enhanced MRI to generate angiograms, and surgical thresholds are based on diameters and growth rates in the ascending aorta. The goal of this project is to develop a high-resolution self-navigating bSSFP sequence and then combine it with 4D flow data in an automated pipeline to allow improved characterization of the anatomy and hemodynamics of the aorta. While 4D flow, a method pioneered in our lab, enables acquisition of temporally and spatially resolved 3D flow velocity without using contrast, the technique could be improved by incorporating higher-resolution scans with improved blood-tissue contrast. Delineation of the volume of the aorta in patients with AS from 4D flow data alone has also historically proven more challenging due to the presence of a high-speed flow jet. Clinical translation of 4D flow is also limited by a time-intensive analysis workflow, so this project includes both the sequence development aims as well as the goal of developing an automated cloud-based analysis pipeline for the data. Close collaboration with clinicians will ensure that calculated metrics are relevant and presented in a manner that could be useful in the clinical staging or management of these patients. The first aim of this proposal is development and validation of a balanced steady-state free-precession (bSSFP) sequence to collect improved anatomic data with high resolution and blood-tissue contrast to improve diameter measurements of the ascending aorta and enable segmentation of the aorta at several time points in the cardiac cycle. This will allow calculation of relative area change as a surrogate for aortic compliance and examination of the wall shear stress dynamics over the cardiac cycle. The second aim will incorporate this higher-resolution data and 4D flow data into a highly automated pipeline that will enable rapid segmentation of the aorta and calculation of the wall shear stress dynamics and relative area changes. In the third aim, 20 BAV and 20 TAV patients with AS will be recruited from the patient population at Northwestern, then imaged and analyzed using the new protocol. This will demonstrate the feasibility of using the method in a clinical setting, while also contributing to answering the question of if AS is a separate clinical entity in BAV and TAV patients. Clinical collaborators will help guide the project to fulfil the ultimate goal of improving clinical imaging and staging of these complex patients.